1. Field of the Invention
The present invention relates to a method for feeding a yarn to a textile machine for its processing and its arrangement for subsequent use. The invention also relates to a textile machine of the aforestated type in which said method is implemented.
2. Description of the Related Art
A textile machine of the aforesaid type, such as a texturizing-interlacing, interlacing or doubling machine, is known to operate on a yarn comprising at least two threads which are secured together (for example interlaced) in order to be collected on a support (a bobbin or spool) for subsequent use in producing an article in a corresponding different textile machine.
Such known textile machines for transforming textile fibres or yarns combine several identical or different textile fibres or yarns in order to transform the group of fibres or yarns into a yarn or fibre having characteristics which are a combination of the characteristics of each fibre or yarn combined in this manner.
In such machines the production process is normally very lengthy, varying from 30 minutes to more than 60 minutes, depending on the counts processed and on the dimensions of the yarn spool or bobbin produced. The process is also normally highly automated, using autodoffing of the spool produced.
In many of these machines, and in particular in machines for interlacing or texturizing and interlacing a synthetic fibre or thread such as nylon or polyurethane with an elastomeric fibre or thread, this latter is fed to the machine processing region by the so-called Deruile' method, i.e. by unwinding and feeding the yarn from its rotating support bobbin at a speed synchronized with the rate at which the processed yarn is collected on said spool or bobbin. In other words, the bobbin supporting the elastomeric thread rotates about its axis at a speed synchronized with the rotational speed of the bobbin or spool on which the yarn is collected after its processing, said synchronized speed enabling the elastomeric thread to be fed to the machine production region at a constant tension determined on the basis of requirements.
Consequently the ratio of collection speed to elastomer feed speed determines the tension or extension of this latter.
This yarn feeding method presents many limitations related to the modality of continuing yarn feed when the elastomeric thread bobbin runs out. For example, in such machines it is not possible to use the known so-called “head-tail” technique, which when a yarn bobbin has run out enables the production process to continue without interruption because of the presence of a second bobbin, the head of which (i.e. the commencement of the thread supported by it) is linked or rather knotted to the tail of the first (i.e. to the end of the thread supported thereby); the reason for this impossibility is that the threads of these bobbins cannot be knotted together because one of them rotates.
Changing the thread bobbin automatically is extremely complex, costly and limited because when a first bobbin of elastomeric thread runs out it is evidently not possible to automatically start the second at full speed.
Moreover if the elastomeric thread breaks in proximity to its end on the relative bobbin, to prevent its further rapid breakage (with consequent further halting of the textile machine) it is preferred to discard the depleting bobbin for a new bobbin; this evidently results in high costs caused by production discards.
In any event, the known method of feeding the textile machine with the elastomeric thread while maintaining its tension constant by controlling the rotation of the corresponding bobbin never allows complete depletion of the bobbin, with consequent creation of rejects (with their associated costs). This is because the initial layers wound on the preparation bobbin causes it to break the thread on the next before its complete depletion.
For this reason, “Derule'” feed devices require the presence of sensors for monitoring yarn breakage and sensors for indicating the bobbin end. In addition, as a textile machine of the stated type comprises numerous parts (“heads”), each for automatically producing a processed yarn, the number of such “heads” assigned to an operator is very high resulting, in the case of yarn breakage, in prolonged intervention downtimes which can heavily affect final production efficiency levels.